Radiant Barrier Coatings

Radiant barriers versus radiant barrier coatings

Radiant barriers, which were first introduced back in the 1930's, are materials that are installed in buildings to reduce summer heat gain and winter heat loss, thereby decreasing energy usage overall. Many are made of a thin sheet of highly reflective material, usually alluminum that is applied to one or both sides of a substrate material, such as craft paper, film, cardboard, or plywood sheathing. These products are designed to be stapled, taped, or nailed to the underside of a roof or top of a truss or sheeting. Some can be applied only during the construction process.

Radiant barrier coatings, on the other hand, contain microscopic metal particles that reflect radiant energy. They can be easily applied to the underside of roofs or homes and businesses as well as new construction. Most manufacturers suggest using an airless sprayer, although many coatings can be rolled or brushed on as well.

The physics behind these products, some of which are referred to as "interior radiation control coatings" is similar to low e glass and windows with the "e" standing for emissivity.

The Upside of Applying Barrier Coatings

With radiant barrier coatings, installers can get in and out in a couple of hours. Plus, sprayed coatings do not trap moisture like foils are prone to do so. To properly apply radiant barrier paint, spray the roof decks, the rafters, the ridge and any gable ends. You may want to encapulate the entire heat-transferring surface with a low emmissive barrier.

Foil or rolled insulation, on the other hand, can only be applied to the roof decks leaving gaps that are not protected. These rolled goods are not only time consuming and expensive but everywhere you staple or nail becomes a conductive surface.

The Facts

In the real world, the energy savings associated with low e paints are hard to pin down because there are so many variables to consider, such as the color the roof, the presence of trees, how well the home is insulated and so on. Every building is different. But what we see in attic temperature drops range from 10 to 40 degrees F. Some people have reported drops as high as 60 degrees F.

In some areas of the country, homeowners are rewarded for using these products via paybacks by cities. Check with your local codes.

Where They Work Best

Radiant barrier coatings don't have a significant effect on air temperatures on well ventilated attics. They are most effective in

• Locations where there are extreme temperatures in the summer
• Homes with strong western exposure
• Homes that rely heavily on air conditioniong for occupant compfort
• Older homes
• Older homes with inadequte insulation
• Homes with dark roofing materials

These coatings will last as long a substrate are kept in good conditions. If the areas are damaged, the coating should be reapplyed to maximize effeciency. These coatings can last a lifetime. The emissivity values are still the same as the day it is installed.

For more information on radiant barrier coatings, visit http://www.sherwin-williams.com. You'll find the coating listed under "Architectural Paints, Stains, and Primers" or search for "radiant barrier coatings."